Add timing prints to object group to get a baseline.

runtime/observatory/lib/object_graph.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library object_graph;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:typed_data';
 
@@ skipping 636 matching lines @@
             }
           }
         }
         if (newDomIndex != 0 && domByPOI[curPostOrderIndex] != newDomIndex) {
           domByPOI[curPostOrderIndex] = newDomIndex;
           changed = true;
         }
       }
     }
 
+    Logger.root.info("Start remap dominators");
+
     // Reindex doms by id instead of post order index so we can throw away
     // the post order arrays.
     var domById = new Uint32List(N + 1);
     for (var id = 1; id <= N; id++) {
       domById[id] = postOrder[domByPOI[postOrderIndex[id]]];
     }
 
+    Logger.root.info("End remap dominators");
+
     domById[root] = 0;
 
     _doms = domById;
   }
 
   void _calculateRetainedSizes() {
     var N = _N;
 
     var size = 0;
     var positions = _positions;
@@ skipping 17 matching lines @@
     for (var o = 0; o < (N - 1); o++) {
       var i = postOrderOrdinals[o];
       assert(i != 1);
       retainedSizes[doms[i]] += retainedSizes[i];
     }
 
     _retainedSizes = retainedSizes;
     _size = size;
   }
 }